The Democratic Party didn't corrupt democracy by choosing Kamala Harris.

Joe Biden's candidacy for reelection was never seriously contested. The party held primaries anyway, which were all over by early June. It was a Biden/Harris ticket. In late June, Biden performed badly in a debate with Trump, raising public skepticism about his cognitive capacity and general health as an 81-year-old. The party chose to elevate Harris in large part because she was already Biden's running mate and thus his campaign money was already in her name. She moved from 2nd place to 1st place on her own ticket. A political party is empowered to make choices like this, and when it does so, it may be safeguarding democracy, not corrupting it. You and many others may not like the candidates or the process, but that doesn't mean the process is corrupt.

You know all this.